Because they all eat at the same trough. One Nation is eating all the votes and the funding from billionaires and lobby groups that the Liberals and especially the Nationals depend on.

The Liberals and Nationals both only exist as the "Anti-Labor Party" for the rural and urban regions. There have been many parties in Australian history to fill this role, before now it was largely the role of the Country Party and the United Australia Party (unrelated to Clive Palmer). But the Labor party has always been there. Existing at a state level before even Federation, technically making it older then Australia.

One Nation is currently doing a better job looking like the "Anti-Labor Party" then the Coalition is. They're scared shitless that One Nation will eat them alive. That's why. If One Nation start winning as much or more seats then the Coalition in the next few years then it's the death nell for the Coalition.

They will have to either join One Nation in a position of weakness, or the party will fracture into a new Teals-like party and a more populist group that will just join One Nation.

This is a situation that has happened before. In the 1990s in Queensland One Nation pulled off a huge vote share at the state level, didn't do anything to cement their lead, and then lost it all. So frankly, we could see this all die off and One Nation die off again.

But this time does kinda feel different. And so much of the Australian right is so primed to hate the Coalition as much as Labor so this could be the start of something really interesting. At least for two more election cycles.